1. Field
The following descriptions relates to a ferrite magnet and a manufacturing method thereof.
2. Background
Soft ferrite refers to a material in which the speed of magnetization is fast even with a slight magnetic field to suddenly saturate the magnetization of the material and also erasing or inverting residual magnetization can be sufficiently accomplished even with a weak magnetic field, and due to such characteristics it is mostly used for devices for filtering or amplifying signals.
Hard ferrite typically refers to a permanent magnet made of ferrite, which has a lot of applications because a strong magnetic field in an inverse direction is required while not requiring voltage application even when removing or inverting residual magnetization, and a constant magnetic field can be generated while not generating heat in itself.
The application of ferrite are made through molding and sintering, and have been used in the broad fields in the aspect of allowing various shapes and requiring a low cost.
Soft ferrite has been used for deflection yokes (DYs) and fly back transformers (FBTs) which are components for Braun tube to enhance the function of electronic deflection and power supply devices. In recent years, soft ferrite has been mostly used in the fields of IMT related communication cores and electromagnetic interference (EMI) cores for absorbing electromagnetic waves and removing noises in addition to home appliance industries such as flat televisions (TVs), digital televisions (TVs), and the like.
Hard ferrite is mostly applicable to electromechanical energy conversions such as a speaker, a permanent magnet motor, a moving coil type device, a magnetic generator, microphone, and the like, and also used for a storage media, and the like.
In order to apply such a ferrite magnet to various fields, it is important to obtain fine single domain powder having an excellent dispersibility.
There has been an attempt for obtaining fine single crystalline ferrite magnetic powder by adding salt, a technology for adding a large amount of sodium chloride or potassium chloride on the basis of a solid state reaction method to synthesize barium ferrite (Ba-ferrite) has been disclosed in the Korean Patent Registration No. 10-0554500.
The foregoing method may include the processes of mixing a raw material with salt according to the objective material and characteristic to correspond to a stoichiometric ratio so as to synthesize ferrite precursor powder, and performing a heat treatment for crystallization and then removing salt.
According to the foregoing method, it may be possible to produce small particles less than 100 nm, but the cohesion of particles may easily occur due to the characteristics of ferrite magnetic particles during the process of removing salt.
Furthermore, even though fine particles are produced through the above complicated process, it may be impossible to prevent particle growth during the sintering process. The problems due to the manufacturing method may cause an increase of the process cost as well as the deterioration of magnetic characteristics.
Sodium chloride or potassium chloride may be added to attempt a ferrite magnetic powder synthesis to obtain fine particles, but the molding and sintering processes are carried out subsequent to removing molten salt to form magnets, and thus there still remain problems in that it is difficult to suppress the growth of ferrite magnetic particles, and also the alignment of magnetic nanoparticles required to maximize magnetization cannot be easily achieved.